Problem: Simplify the following expression: $p = \dfrac{9}{2n + 2} \div \dfrac{4}{10n}$
Dividing by an expression is the same as multiplying by its inverse. $p = \dfrac{9}{2n + 2} \times \dfrac{10n}{4}$ When multiplying fractions, we multiply the numerators and the denominators. $p = \dfrac{ 9 \times 10n } { (2n + 2) \times 4}$ $p = \dfrac{90n}{8n + 8}$ Simplify: $p = \dfrac{45n}{4n + 4}$